Micro or nano porous membrane, manufacturing method of same, porous resin membrane complex, and filter element

Abstract

The present disclosure relates to a micro or nano porous membrane composed of a stretched membrane of a fluororesin membrane, wherein the fluororesin membrane contains sintered bodies of a plurality of core-shell particles containing fluororesins, wherein the core-shell particles include cores and shells covering outer surfaces of the cores, wherein an average particle size of the core-shell particles before being sintered is greater than or equal to 100 nm and less than or equal to 1,000 nm, wherein a ratio of a volume of the shells to a volume of the cores in the core-shell particles before being sintered is greater than or equal to 2/98 and less than or equal to 50/50, wherein a fluororesin of the cores is a tetrafluoroethylene-hexafluoropropylene copolymer, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a combination thereof, and a fluororesin of the shells is polytetrafluoroethylene, and wherein a first heat of fusion of the fluororesins in the core-shell particles is less than or equal to 68 J/g.

The invention claimed is: 
     
       1. A micro or nano porous membrane composed of a stretched membrane obtained by stretching a non-porous membrane material of fluororesins,
 wherein the non-porous membrane material of the fluororesins is a sintered body obtained by shaping a plurality of core-shell particles containing the fluororesins into a membrane, and by sintering the plurality of core-shell particles by heating the membrane obtained by the shaping to its melting point or more, 
 wherein the core-shell particles include cores and shells covering outer surfaces of the cores, 
 wherein an average particle size of the core-shell particles before being sintered is greater than or equal to 100 nm and less than or equal to 1,000 nm, 
 wherein a ratio of a volume of the shells to a volume of the cores in the core-shell particles before being sintered is greater than or equal to 2/98 and less than or equal to 50/50, 
 wherein a fluororesin of the cores is a tetrafluoroethylene-hexafluoropropylene copolymer or a combination of the tetrafluoroethylene-hexafluoropropylene copolymer and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and a fluororesin of the shells is polytetrafluoroethylene, 
 wherein the tetrafluoroethylene-hexafluoropropylene copolymer does not include any monomer other than tetrafluoroethylene and hexafluoropropylene, 
 wherein the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer does not include any monomer other than tetrafluoroethylene and perfluoroalkyl vinyl ether, 
 wherein a first heat of fusion of the fluororesins in the core-shell particles is less than or equal to 68 J/g, and 
 a Gurley in the micro or nano porous membrane is 25 seconds or less. 
 
     
     
       2. The micro or nano porous membrane according to  claim 1 , wherein a permeability index, represented by (membrane thickness (μm)×air permeability rate (mL/sec/cm 2 ))/(average equivalent circle diameter of pores (μm)) 2 , is greater than or equal to 100. 
     
     
       3. A method of manufacturing a micro or nano porous membrane composed of a stretched membrane obtained by stretching a non-porous membrane material of fluororesins, the method comprising:
 shaping a plurality of core-shell particles containing the fluororesins into a membrane; 
 sintering the plurality of core-shell particles by heating the membrane obtained by the shaping to its melting point or more to obtain a sintered body, which is the non-porous membrane material of the fluororesins; and 
 stretching the non-porous membrane material of the fluororesins obtained by the sintering, 
 wherein the core-shell particles include cores and shells covering outer surfaces of the cores, 
 wherein an average particle size of the core-shell particles before the sintering is greater than or equal to 100 nm and less than or equal to 1,000 nm, 
 wherein a ratio of a volume of the shells to a volume of the cores in the core-shell particles before the sintering is greater than or equal to 2/98 and less than or equal to 50/50, 
 wherein a fluororesin of the cores is a tetrafluoroethylene-hexafluoropropylene copolymer or a combination of the tetrafluoroethylene-hexafluoropropylene copolymer and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and a fluororesin of the shells is polytetrafluoroethylene, 
 wherein the tetrafluoroethylene-hexafluoropropylene copolymer does not include any monomer other than tetrafluoroethylene and hexafluoropropylene, 
 wherein the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer does not include any monomer other than tetrafluoroethylene and perfluoroalkyl vinyl ether, 
 wherein a first heat of fusion of the fluororesins in the core-shell particles is less than or equal to 68 J/g, and 
 a Gurley in the micro or nano porous membrane is 25 seconds or less. 
 
     
     
       4. The method of manufacturing a micro or nano porous membrane according to  claim 3 , wherein a permeability index, represented by (membrane thickness (μm)×air permeability rate (mL/sec/cm 2 ))/(average equivalent circle diameter of pores (μm)) 2 , is greater than or equal to 100. 
     
     
       5. A porous resin membrane complex comprising:
 a porous support; and
 the micro or nano porous membrane according to  claim 1  fixed on the support. 
 
 
     
     
       6. A filter element comprising: the porous resin membrane complex according to  claim 5 .